4:55 p.m. Turkish PM says all victims killed in the Sultanahmet suicide attack are foreigners while the suicide bomber is an Islamic State of Iraq and the Levant (ISIL) militant.

4:35 p.m. The suicide bomber who committed the attack in Istanbul’s Sultanahmet Square has been identified as Saudi-born Nabil Fadli. Investigations continue to reveal the militant’s connections, Doğan News Agency has reported.

Turkish Deputy Prime Minister Numan Kurtulmuş had announced at a press conference that the suicide bomber was a man of Syrian origin born in 1988.

4:00 p.m. The Council of Europe’s parliamentary assembly president Anne Brasseur has “strongly condemned” the attack in Istanbul while expressing her support for Turkey and condolences to the Turkish people.

“Turkey can count on our support in combating terrorism and violent extremism. It is the duty of all democratic political forces to stand up against radicalisation and the hatred that fuel violent extremism and terrorism,” Brasseur’s statement said.

3:50 p.m. The Greek Ministry of Foreign Affairs has released an official statement on its website, condemning the attack in Istanbul.

“We unequivocally condemn the abhorrent terrorist suicide attack that took place this morning in Istanbul,” the statement said, adding that Greece stands in solidarity with the Turkish people.

3: 40 p.m. Turkish PM Davutoğlu has informed Merkel that most of the victims are German and extended his condolences.

Davutoğlu has reportedly told Merkel that an investigation is being carried out delicately and that all necessary information will be shared with German authorities.

3:20 p.m. NATO Secretary-General Jens Stoltenberg has strongly condemned the terrorist attack in Istanbul and extended his condolences to the families of the victims.

“My thoughts are with those injured, with the Turkish people, and with all the other nations affected,” he said.

“There can be no justification for such attacks. All NATO allies stand united in the fight against all forms of terrorism,” Stoltenberg added.

3:00 p.m. Chancellor Angela Merkel said she was very worried that German citizens might be among the victims and the wounded, Reuters has reported. "International terrorism has shown its ugly face," said Merkel. "We need to act decisively against it."

Meanwhile, German Foreign Minister Frank-Walter Steinmeier said that German citizens may have died in an attack in Istanbul, and that Germans were almost certainly among the injured.

"By now we have to assume that also Germans have been injured in this terror attack," Steinmeier said at a news conference in Berlin. "We also can't exclude that Germans are among the dead."

2: 40 p.m. Italy’s prime minister also expressed support for Turkey after the “agonizing” attack in Sultanahmet Square.

Most of the victims are foreigners, Deputy PM Numan Kurtulmuş has said, adding that two of the 15 hospitalized victims are in critical condition.

He confirmed that it was a suicide attack and that the suspect was of Syrian origin.

Systematic attacks have continued in Turkey since June 5 last year, Kurtulmuş said, asking for more international support and more coordination in the struggle against terrorism.

2:00 p.m. Main opposition Republican People’s Party (CHP) leader Kemal Kılıçdaroğlu condemned the attack in a message posted to his official Twitter account.

“Those who aimed at our country with the treacherous attack in Sultanahmet will never reach their goal. I condemn terror and those who get nourished by terror with hatred,” Kılıçdaroğlu said.

Later, addressing a parliamentary group meeting of his party, he said the blast proved that the ruling Justice and Development Party (AKP) is not able to govern the party is getting it into more and more troubles instead.

“A bomb explodes at the heart of tourism, in Sultanahmet and you have no measures taken. Then what do you do? You impose a ban on reporting even before ambulances arrive [on the scene]. This government is not able to rule the country,” he said.

1:45 p.m. The European Union has also commented on Sultanahmet explosion in a statement by High Representative/Vice-President Federica Mogherini and Commissioner Johannes Hahn.

"Turkey has once again been targeted by a terrorist attack, this time on Sultanahmet Square in the heart of Istanbul's tourist district. The EU extends sincere condolences to the families of the victims killed in the bomb attack today and wishes a speedy recovery to those injured.

The EU and Turkey stand united against all forms of terrorism. The fight against terrorism was recognised as a priority at the EU-Turkey Summit on 29 November 2015 and we must step up our efforts in this regard in full respect of our obligations under international law, including human rights and humanitarian laws," the statement read.

1:30 p.m. Turkish President Recep Tayyip Erdoğan has said Sultanahment explosion was a suicide attack of Syrian origin

1:15 p.m. Former Turkish President Abdullah Gül expressed his condolences to the families of the attack’s victims and urged unity against terror.

“Our citizens should support the government and the state in all related manners and act in accordance to its demands,” Gül has told reporters

1: 10 p.m. Peoples’ Democratic Party (HDP) co-leader Selahattin Demirtaş extended condolence to families of the victims who lost their lives in the blast which he called a “brutal massacre.”

“We condemn the massacre in Sultanahmet. We will not stop following [the blast] so as not to let it be left in the dark and to reveal the ones responsible,” Demirtaş said, while addressing a parliamentary group meeting of his party.

1:00 p.m. Justice and Development Party (AKP) spokesperson Ömer Çelik has posted a tweet condemning the “vile” attack in Sultanahmet.

“May God rest the victims’ souls,” the tweet said, while wishing a quick recovery to all those wounded in the explosion.

12.50 Security authorities believe an Islamic State of Iraq and the Levant-linked suicide bomber was behind the explosion in Sultanahmet, daily Hürriyet has reported.

Authorities are focusing on ISIL links because tourists and civilians were targeted in a touristic area.

12.21 Security meeting to be held at Çankaya Palace under the chairmanship of PM Davutoğlu.